I'm planning to add an amplifier and upgrade the stock speakers from the base six-speaker configuration. So far, Focal and JL seem to be contenders for quality replacements. I believe I'll need a pair of coaxials (non-components) for the front in four-inch size, but I can't seem to find the ones that are sure to fit. As for the back seat, I'm not sure what type of four-inch replacements would be best. And as for the subs under the seats, I'm thinking of just deleting those and adding a meatier sub in the boot. After spending 8 years of listening to a JL system, the stock speakers are really basic--not the kind of clarity, separation, and body of sound that I got used to. Who's doing audio upgrades and what are your insights and advice? Thanks, Chuck